1. Field of the Invention
The present invention relates to an optical amplifying medium component and an optical fiber amplifier comprising the optical amplifying medium component. Especially, an optical amplifying medium component comprising a rare-earth doped fiber as an optical amplifying medium and having the function of maintaining the temperature of such a fiber constant.
2. Description of the Related Art
In recent years, Wavelength Division Multiplexing (WDM) technology has been developed and proceeded toward practical utilization to cope with growing demand for network access and transmission products in telecommunications as the development of Internet has surged forward. The WDM system allows an increase in the transmission capacity of a single optical fiber transmission line by multiplexing a plurality of signal light beams having different wavelengths onto the optical fiber over a predetermined wavelength band region.
The WDM system can easily increase the transmission capacity of the optical fiber by extending the range of bandwidths to increase the number of optical signals to be multiplexed. In this case, the optical fiber amplifier is required to be one having flat wavelength characteristics of gain (i.e., the increase in the amplitude of a signal is constant) with respect to the broad bandwidth. For instance, optical signals at a wavelength band of 1550 nm is generally used. In this case, an erbium-doped optical fiber (EDF) is used as an optical amplifying medium.
In the first aspect of the present invention, an optical amplifying medium component includes an optical amplifying medium for amplifying signal light, a first substrate on which the optical amplifying medium is placed, a second substrate opposite to the first substrate to sandwich the optical amplifying medium between the first substrate and the second substrate, and a first temperature control element for controlling the temperature of the first element.
Here, the optical amplifying medium component may further include a second temperature control element for controlling the second substrate.
The optical amplifying medium may be a rare-earth element doped optical fiber.
The optical amplifying medium component may further include a temperature-detecting device for detecting temperature at a predetermined place in the proximity of the optical amplifying medium.
The rare-earth element doped optical fiber may be placed in a plane without bending and crossing; and
the rare-earth element doped optical fiber and the temperature-detecting device are sandwiched between the first substrate and the second substrate.
In the second aspect of the present invention, an optical fiber amplifier includes an optical amplifying medium component, a pumping light source for producing pumping light, and an optical multiplexer for multiplexing the pumping light with signal light to send them to the optical amplifying medium. The optical amplifying medium component includes an optical amplifying medium for amplifying signal light, a first substrate on which the optical amplifying medium is placed, a second substrate opposite to the first substrate to sandwich the optical amplifying medium between the first substrate and the second substrate, and a first temperature control element for controlling the temperature of the first element.
The optical amplifying medium component may further comprise: a second temperature control element for controlling the second substrate.
Here, the optical amplifying medium may be a rare-earth element doped optical fiber.
The optical amplifying medium component may further comprise: a temperature control circuit for adjusting temperature at a predetermined place in the proximity of the optical amplifying medium. If the relationship between the temperature and the wavelength characteristics of gain are investigated in advance, a temperature control circuit may be used for actively adjusting the temperature of the optical amplification medium in the optical amplifying medium component. Therefore, it allows to keep the such a medium entirely at a predetermined temperature so as to obtain desired wavelength characteristics of gain thereof. In this case, the action of gain equalization can be achieved.